Fuel cell system

Abstract

The fuel cell system includes a fuel cell (FC) (1), a motor (2), a first power line (3) connecting the FC (1) and the motor (2), a storage battery (4), and a second power line (5) connecting the storage battery (4) and the first power line (3). The first power line (3) is provided with an FC relay (7) for opening and closing the first power line (3), and the second power line (5) is provided with a battery relay (8) for opening and closing the second power line (5). The fuel cell system is provided with a control means (ECU) (10) for controlling the opening and closing of the two relays (7, 8) so as to limit the upper limit of the output of the FC (1) and the storage battery (4), and the ECU (10) controls the closing of the two relays (7, 8) when the monitored charging rate of the storage battery (4) is less than 30%.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell system including: a fuel cell used as a power source for an electric vehicle or the like and connected to a load device; and a battery provided in a discharge path from the fuel cell to the load device and connected in parallel with the fuel cell. Background Art

[0002] As a conventional technology of this type, for example, the "fuel cell system" described in Patent Document 1 below is known. This system includes a fuel cell, a load device, a first wiring connecting the fuel cell and the load device, a battery, and a second wiring connected from the battery to the first wiring. A voltage converter is provided on the first wiring to convert the voltage between the terminal voltage of the fuel cell and the voltage on the load device side.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-228294 Summary of the Invention

[0006] Problems to be solved by the invention

[0007] However, in the fuel cell system described in Patent Document 1, while the voltage converter can control the power supplied to the load device to prevent it from exceeding the fuel cell's upper power limit, this itself can increase system costs and size. In recent years, simple and inexpensive fuel cell systems have been desired for installation in electric vehicles and the like.

[0008] The disclosed technology has been developed in view of the above circumstances, and an object of the present disclosure is to provide a simple and more inexpensive fuel cell system capable of controlling the power supplied to a load device without using a voltage converter to avoid exceeding the upper power limits of the fuel cell and battery.

[0009] Solutions for solving problems

[0010] (1) In order to achieve the above-mentioned purpose, a technical solution of the technology disclosed in the present application is a fuel cell system, which comprises: a fuel cell; a load device; a first power line connecting the fuel cell and the load device; a battery; and a second power line connecting the battery and the first power line. The main purpose of the fuel cell system is that the fuel cell system comprises: a first relay, which is arranged on the first power line and is used to open and close the first power line; and a second relay, which is arranged on the second power line and is used to open and close the second power line.

[0011] According to the configuration (1) above, the power supply from the fuel cell to the load device is turned on and off by opening and closing the first relay, and the power supply from the battery to the load device is turned on and off by opening and closing the second relay. Therefore, by appropriately controlling the opening and closing of the first and second relays, power supply to the load device can be adjusted to match the output states of the fuel cell and the battery.

[0012] (2) In order to achieve the above-mentioned purpose, it is preferred that, in the structure of the above-mentioned (1), the fuel cell system comprises: a relay control unit which controls the opening and closing of the first relay and the second relay to limit the upper limit of the output of the fuel cell and the output of the battery; and a charging rate monitoring unit which is used to monitor the charging rate of the battery, the relay control unit controls the closing of the first relay and the second relay when the charging rate of the battery monitored by the charging rate monitoring unit is less than a third specified value.

[0013] According to the configuration of (2), in addition to the function of the configuration of (1), when the charge rate of the monitored battery is less than the third predetermined value, the relay control unit controls the first relay and the second relay to close, thereby returning the outputs of the fuel cell and the battery to their natural states. As a result, the outputs of the fuel cell and the battery approach their permissible operating ranges.

[0014] (3) In order to achieve the above-mentioned purpose, it is preferred that, in the structure of the above-mentioned (2), for the relay control unit, (i) when the monitored charging rate is greater than or equal to the first prescribed value, the first relay and the second relay are controlled to be open, (ii) when the monitored charging rate is greater than or equal to the second prescribed value and less than the first prescribed value, the first relay is controlled to be open and the second relay is controlled to be closed, (iii) when the monitored charging rate is greater than or equal to the third prescribed value and less than the second prescribed value and the load device is in a braking period, the first relay and the second relay are controlled to be closed, and (iv) when the monitored charging rate is greater than or equal to the third prescribed value and less than the second prescribed value and the load device is in a regeneration period, the first relay is controlled to be open and the second relay is controlled to be closed, with the relationship of the first prescribed value > the second prescribed value > the third prescribed value.

[0015] According to the configuration of (3), in addition to the function of the configuration of (2), (i) when the monitored charge rate is equal to or greater than the first predetermined value, the relay control unit controls the first relay and the second relay to open, thereby reducing the output of the fuel cell and the output of the battery to zero. (ii) when the monitored charge rate is equal to or greater than the second predetermined value and less than the first predetermined value, the relay control unit controls the first relay to open and the second relay to close, thereby reducing the output of the fuel cell and the output of the battery to a natural state. (iii) when the monitored charge rate is equal to or greater than the third predetermined value and less than the second predetermined value and the load device is in a braking period, the relay control unit controls the first relay and the second relay to close, thereby reducing the output of the fuel cell and the output of the battery to a natural state. (iv) when the monitored charge rate is equal to or greater than the third predetermined value and less than the second predetermined value and the load device is in a regeneration period, the relay control unit controls the first relay to open and the second relay to close, thereby reducing the output of the fuel cell and the output of the battery to zero. Therefore, through the control of (i) to (iv) above, the output of the fuel cell and the output of the battery are brought close to the allowable operating range.

[0016] (4) In order to achieve the above-mentioned object, it is preferred that, in the structure of (2) or (3) above, when the monitored charging rate is smaller than a third specified value, the relay control unit corrects the indicated output value of the load device in accordance with the charging rate to suppress the indicated output value.

[0017] According to the configuration of (4), in addition to the operation of the configuration of (2) or (3), when the monitored charging rate is less than the third predetermined value, the relay control unit corrects the indicated output value of the load device in accordance with the charging rate to suppress the indicated output value. Therefore, when the charging rate is less than the third predetermined value, the supply of electric power from the fuel cell and the battery to the load device is precisely suppressed in accordance with the charging rate.

[0018] (5) In order to achieve the above-mentioned object, it is preferred that, in the structure of the above-mentioned (1), the fuel cell system has a load output determination unit for determining the indicated output value of the load device, and the load output determination unit determines the indicated output value by subtracting the reduced output value of the fuel cell and the reduced output value of the battery from the required output value of the load device.

[0019] According to the configuration of (5), based on the effect of the configuration of (1), the indicated output value of the load device is determined in accordance with the output capacity of the fuel cell and the output capacity of the battery at that time.

[0020] Effects of the Invention

[0021] According to the configuration of (1) above, a simple and more inexpensive fuel cell system can be provided that can control the power supplied to the load device without using a voltage converter so as not to exceed the upper power limits of the fuel cell and the battery.

[0022] According to the configuration of (2), in addition to the effect of the configuration of (1), when the charge rate of the battery decreases, the upper limits of the output of the fuel cell and the output of the battery can be restricted.

[0023] According to the configuration of (3), in addition to the effects of the configuration of (2), the upper limits of the output of the fuel cell and the output of the battery can be more precisely limited in accordance with changes in the charge rate of the battery.

[0024] According to the above configuration (4), in addition to the effects of the above configuration (2) or (3), when the charge rate of the battery is further reduced, the upper limits of the output of the fuel cell and the output of the battery can be more precisely limited.

[0025] According to the structure of (5) above, in addition to the effect of the structure of (14) above, it is possible to prevent an excessive output load from being applied to the fuel cell and the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a block diagram showing a fuel cell system mounted on an electric mobility vehicle according to one embodiment.

[0027] Figure 2 This is a flowchart showing an example of the content of “power supply control” according to one embodiment.

[0028] Figure 3 This is an output correction value map that is referred to in order to determine an output correction value according to the charging rate of the battery in one embodiment. DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment in which a fuel cell system is embodied as a small electric vehicle (electric scooter) will be described in detail with reference to the accompanying drawings.

[0030] [Overview of the fuel cell system]

[0031] exist Figure 1 , a block diagram shows a fuel cell system installed in an electric mobility vehicle according to this embodiment. This fuel cell system includes a fuel cell (FC) 1, an electric motor 2, a first power line 3 connecting the FC 1 and the motor 2, a battery 4, and a second power line 5 connecting the battery 4 and the first power line 3.

[0032] FC1 is an electrochemical cell that converts the chemical energy of fuel and oxidant into electricity through a redox reaction and has a known structure. Motor 2 has a known structure and serves as an example of a "load device" in the disclosed technology. In this embodiment, battery 4 is composed of a rechargeable and dischargeable secondary battery.

[0033] In the present embodiment, a diode 6 for rectification and an FC relay 7 for opening and closing the first power line 3 are provided in series on the first power line 3. The FC relay 7 is equivalent to the "first relay" of the disclosed technology. The second power line 5 is connected to the portion of the first power line 3 between the diode 6 and the motor 2. A battery relay 8 is provided on the second power line 5 for opening and closing the second power line 5. The battery relay 8 is equivalent to the "second relay" of the disclosed technology. The FC relay 7 and the battery relay 8 each have a known structure that can be opened and closed by being operated electrically. The fuel cell system also includes an electronic control unit (ECU) 10 for controlling the opening and closing of each relay 7, 8. The ECU 10 has a known structure including a central processing unit (CPU) for performing calculation processing, a memory, and input and output ports. The ECU 10 is equivalent to an example of a "relay control unit" of the disclosed technology.

[0034] In this embodiment, the motor 2 is drivingly coupled to the electric scooter's drive wheels 11. An accelerator pedal sensor 12 is connected to the ECU 10. The accelerator pedal sensor 12 detects the angle of a pedal 13 operated by the user of the electric scooter as the accelerator pedal opening and outputs the detection signal to the ECU 10.

[0035] ECU 10 is electrically connected to battery 4 and monitors the state of charge (SOC) of battery 4. ECU 10 also serves as an example of a "charge rate monitoring unit" in the disclosed technology. Furthermore, ECU 10 is electrically connected to FC1 and battery 4 and measures the current and voltage of FC1 and the current and voltage of battery 4. ECU 10 also serves as an example of a "current and voltage measurement unit."

[0036] Furthermore, the ECU 10 determines an instructed output value (motor instructed output value) of the motor 2 as a load device, and corresponds to an example of “load output determining means” in the disclosed technology.

[0037] Here, in order to limit the upper limits of the output of FC1 and the output of battery 4, it is necessary to limit the output of motor 2. Therefore, in this embodiment, ECU 10 executes the following "power supply control" when the electric mobility vehicle is running.

[0038] [Regarding power supply control]

[0039] exist Figure 2, an example of the content of the “power supply control” according to the present embodiment stored in the memory of the ECU 10 is shown by a flowchart.

[0040] When the processing transfers to this routine, in step 100, the ECU 10 obtains the measured current value (FC current value) FCCV and voltage value (FC voltage value) FCVV of FC1, and the current value (battery current value) BTCV and voltage value (battery voltage value) BTVV of the battery 4.

[0041] Next, in step 110, the ECU 10 calculates the actual output value of FC1 (FC actual output value) FCRO and the actual output value of battery 4 (battery actual output value) BTRO. The ECU 10 can determine the FC actual output value FCRO based on the measured FC current value FCCV and FC voltage value FCVV. Furthermore, the ECU 10 can determine the battery actual output value BTFCRO based on the measured battery current value BTCCV and battery voltage value BTVV.

[0042] Next, in step 120, the ECU 10 sets the result of subtracting the upper limit output value of FC1 (FC upper limit output value) FCUO from the actual FC output value FCRO, which is a value greater than or equal to "0", as the decrement output value of FC1 (FC decrement output value) FCDO. The FC upper limit output value FCUO is a pre-determined value.

[0043] Next, in step 130, ECU 10 sets the value obtained by subtracting the upper limit output value (battery upper limit output value) BTUO of battery 4 from the actual battery output value BTRO, which is a value greater than or equal to "0", as the reduced output value (battery reduced output value) BTDO of battery 4. Battery upper limit output value BTUO is a pre-determined set value.

[0044] Next, in step 140, the ECU 10 applies an upper limit to the commanded output value (motor commanded output value) MTCO of motor 2 based on the result obtained by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor 2's required output value (motor required output value) MTRO. In other words, the motor output is limited based on the battery output and the FC output.

[0045] Next, in step 150 , the ECU 10 acquires the charge rate SOC of the battery 4 .

[0046] Next, in step 160 , ECU 10 determines whether the SOC is 80% or higher. "80%" is an example of the "first predetermined value" in the disclosed technology. If the result of this determination is affirmative, ECU 10 proceeds to step 170 ; if not, the process proceeds to step 190 .

[0047] In step 170 , the ECU 10 controls the FC relay 7 and the battery relay 8 to be turned on.

[0048] Next, in step 180 , the ECU 10 controls the motor 2 according to the motor command output value MTCO and temporarily ends the subsequent processing.

[0049] On the other hand, when the process moves from step 160 to step 190, the ECU 10 determines whether the SOC is greater than or equal to 70% and less than 80%. "70%" is an example of the "second predetermined value" in the disclosed technology. If the result of this determination is affirmative, the ECU 10 moves the process to step 200; if the result of this determination is negative, the process moves to step 210.

[0050] In step 200 , the ECU 10 performs an opening control on the FC relay 7 and a closing control on the battery relay 8 , and then shifts the process to step 180 .

[0051] Meanwhile, in step 210, ECU 10 determines whether the SOC is greater than or equal to 30% and less than 70%. "30%" corresponds to an example of the "third predetermined value" (first predetermined value > second predetermined value > third predetermined value) in the disclosed technology. If the result of this determination is affirmative, ECU 10 proceeds to step 220; if not, the process proceeds to step 240.

[0052] In step 220 , the ECU 10 performs closing control on the FC relay 7 and the battery relay 8 during braking of the motor 2 .

[0053] Next, in step 230 , the ECU 10 controls the FC relay 7 to be open and the battery relay 8 to be closed during the regeneration period of the motor 2 , and then shifts the processing to step 180 .

[0054] On the other hand, in step 240 , the ECU 10 determines whether the charge rate SOC is less than 30%. If the determination result is affirmative, the ECU 10 proceeds to step 250 , and if the determination result is negative, the ECU 10 proceeds to step 180 .

[0055] In step 250 , the ECU 10 controls the FC relay 7 and the battery relay 8 to close.

[0056] Next, in step 260, the ECU 10 calculates an output correction value KO according to the charge rate SOC. The ECU 10 calculates the output correction value KO according to the charge rate SOC. Figure 3 The output correction value map shown above can determine the output correction value KO according to the charge rate SOC.

[0057] Next, in step 270 , the ECU 10 sets the motor requested output value MTRO as the motor command output value MTCO, or sets the result obtained by multiplying the motor command output value MTCO by the output correction value KO as the motor command output value MTCO, and then transfers the process to step 180 .

[0058] According to the above power supply control, when the monitored charge rate SOC of the battery 4 is less than 30% (third predetermined value), the ECU 10 controls the FC relay 7 and the battery relay 8 to close so as to limit the upper limits of the output of the FC1 and the output of the battery 4.

[0059] In addition, according to the above-mentioned power supply control, ECU10 (i) controls the FC relay 7 and the battery relay 8 to be open when the monitored charging rate SOC is "80%" (the first specified value) or more, (ii) controls the FC relay 7 to be open and controls the battery relay 8 to be closed when the monitored charging rate SOC is "70%" (the second specified value) or more and less than "80%", (iii) controls the FC relay 7 and the battery relay 8 to be closed when the monitored charging rate SOC is "30%" or more and less than "70%" and the motor 2 is in the braking period, (iv) controls the FC relay 7 to be open and controls the battery relay 8 to be closed when the monitored charging rate SOC is "30%" or more and less than "70%" and the motor 2 is in the regeneration period.

[0060] Furthermore, according to the above-described power supply control, when the monitored charge rate SOC is less than 30%, the ECU 10 corrects the motor command output value MTCO of the motor 2 according to the charge rate SOC to suppress the motor command output value MTCO.

[0061] Furthermore, according to the above-described electric power supply control, the ECU 10 determines the motor command output value MTCO by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor required output value MTOR.

[0062] [Regarding the functions and effects of fuel cell systems]

[0063] According to the structure of the fuel cell system of this embodiment described above, the power supply from FC1 to motor 2 is turned on and off by opening and closing FC relay 7, and the power supply from battery 4 to motor 2 is turned on and off by opening and closing battery relay 8. Therefore, by appropriately controlling the opening and closing of FC relay 7 and battery relay 8, power can be supplied to motor 2 in accordance with the output status of FC1 and battery 4. This allows for a simple and cost-effective fuel cell system that can control the power supply to motor 2 without using a voltage converter to prevent it from exceeding the upper power limits of FC1 and battery 4.

[0064] According to the configuration of this embodiment, when the monitored SOC of battery 4 falls below 30% (the third predetermined value), ECU 10 controls FC relay 7 and battery relay 8 to close, thereby returning the outputs of FC1 and battery 4 to their natural states. Consequently, the outputs of FC1 and battery 4 approach their permissible operating ranges. Consequently, as the SOC of battery 4 decreases, the upper limits of the outputs of FC1 and battery 4 can be limited.

[0065] According to the configuration of this embodiment, (i) when the monitored state of charge (SOC) is greater than or equal to 80% (a first predetermined value), ECU 10 controls FC relay 7 and battery relay 8 to open, thereby reducing the output of FC1 and the output of battery 4 to zero. (ii) When the monitored state of charge (SOC) is greater than or equal to 70% (a second predetermined value) and less than 80%, ECU 10 controls FC relay 7 to open and battery relay 8 to close, thereby reducing the output of FC1 to zero and placing the output of battery 4 in a natural state. (iii) When the monitored state of charge (SOC) is greater than or equal to 30% (a third predetermined value) and less than 70% and motor 2 is braking, ECU 10 controls FC relay 7 and battery relay 8 to close, thereby reducing the output of FC1 and the output of battery 4 to a natural state. (iv) When the monitored SOC is between 30% and 70% and the motor 2 is regenerating, the ECU 10 controls the FC relay 7 to open and the battery relay 8 to close, thereby reducing the output of the FC1 to zero and bringing the output of the battery 4 to its natural state. Consequently, the outputs of the FC1 and the battery 4 approach their permissible operating ranges. Therefore, the control steps (i) to (iv) above enable more precise upper limits on the outputs of the FC1 and the battery 4, corresponding to changes in the SOC of the battery 4.

[0066] According to the configuration of this embodiment, when the monitored state of charge (SOC) is less than 30%, ECU 10 corrects the power requirement of motor 2 in accordance with the SOC to suppress the power requirement. Therefore, when the charge rate is less than a third predetermined value, the power supply from the fuel cell and battery to the load device (motor command output value MTCO) is precisely suppressed in accordance with the charge rate. Consequently, as the SOC of battery 4 further decreases, the output of FC1 and the upper limit of battery 4 output can be more precisely limited.

[0067] According to the configuration of this embodiment, the ECU 10 determines the motor command output value MTCO by subtracting the FC reduction output value FCDO and the battery reduction output value BTDO from the motor required output value MTRO. Consequently, the motor command output value MTCO is determined to be consistent with the current output capacity of the FC1 and the output capacity of the battery 4. This prevents excessive output loads on the FC1 and battery 4.

[0068] In addition, the disclosed technology is not limited to the above-described embodiment, and can be implemented by appropriately changing part of the structure within the scope of the disclosed technology.

[0069] For example, in the above-described embodiment, the electric motor 2 is used as the load device, but other electric motors may be used.

[0070] Industrial applicability

[0071] The disclosed technology can be used in a fuel cell system mounted on an electric vehicle.

[0072] Description of Reference Numerals

[0073] 1. FC (fuel cell); 2. Motor (load device); 3. First power line; 4. Battery; 5. Second power line; 7. FC relay (first relay); 8. Battery relay (second relay); 10. ECU (relay control unit, charge rate monitoring unit, load output determination unit).

Claims

1. A fuel cell system comprising: fuel cells; Loading device; a first power line connecting the fuel cell and the load device; batteries; and a second power line connecting the battery and the first power line; The fuel cell system is characterized in that The fuel cell system comprises: a first relay provided on the first power line and configured to open and close the first power line; and The second relay is provided on the second power line and is used to open and close the second power line.

2. The fuel cell system according to claim 1, wherein: The fuel cell system comprises: a relay control unit configured to control the opening and closing of the first relay and the second relay to limit the upper limits of the output of the fuel cell and the output of the battery; and a charging rate monitoring unit for monitoring the charging rate of the battery, The relay control unit performs closing control on the first relay and the second relay when the charging rate of the battery monitored by the charging rate monitoring unit is lower than a third predetermined value.

3. The fuel cell system according to claim 2, wherein: For the relay control unit, (i) when the monitored charging rate is equal to or greater than a first predetermined value, the first relay and the second relay are controlled to be open; (ii) when the monitored charging rate is equal to or greater than a second predetermined value and less than the first predetermined value, the first relay is controlled to be open and the second relay is controlled to be closed; (iii) when the monitored charging rate is equal to or greater than a third predetermined value and less than the second predetermined value and the load device is in a braking period, the first relay and the second relay are controlled to be closed; (iv) when the monitored charging rate is equal to or greater than a third predetermined value and less than the second predetermined value and the load device is in a regeneration period, the first relay is controlled to be open and the second relay is controlled to be closed; The relationship is: the first predetermined value > the second predetermined value > the third predetermined value.

4. The fuel cell system according to claim 2 or 3, characterized in that: When the monitored charging rate is smaller than the third predetermined value, the relay control unit corrects the indicated output value of the load device according to the charging rate so as to suppress the indicated output value.

5. The fuel cell system according to claim 1, wherein: The fuel cell system includes a load output determination unit for determining an instructed output value of the load device. The load output determination unit determines the instructed output value by subtracting a reduced output value of the fuel cell and a reduced output value of the battery from a required output value of the load device.

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